| Author | Message | ||
| Bart Duncan (Bartman)
Registered Member Username: Bartman Post Number: 14 Registered: 11-2007 Posted From: 68.185.135.211 Rating: N/A |
O.K. - I know that when I crank the old 81' Prevost and the PSI levels out about 90 I'm good. BUT... The hissing under my dashboard and above the front passenger tire brings me back to 60 PSI in 5 minutes - I have a problem... My question is How much will the repair cost? Thanks in advance! Bart | ||
| Rob Norgren (Robsedona)
Registered Member Username: Robsedona Post Number: 36 Registered: 11-2007 Posted From: 75.208.25.222  Rating: N/A |
I believe that Leveling out at 90 is also a problem it should be more like 120 or so. 90 is the low limit. To know how much you have to find out what is leaking first! It could be many things depending on the Equipment you have installed IE air gauge, air wipers, air levers. So more info is needed | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 377 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Well, We may be good, but we're not clairvoyant. WHATEVER YOU DO, DON'T GO UNDER A LEAKING AIR RIDE BUS, OR BETWEEN THE TIRES AND THE WHEEL WELLS, WITHOUT BLOCKING IT SECURELY AT THE JACKING POINTS!!! That said, and the reason for it is your life, get out the spray bottle and fill it with a high concentration of dish soap and water, and spray the noisy areas. Then post back and tell us what's blowing bubbles? You might be lucky, and its only two fittings, or some plastic hose. Or the noise over the tire that you won't get to until AFTER you've securely blocked the bus UP, may be an air bag. Air pressure should rise to 120 before the governor unloads the compressor, if your bus doesn't attain 120 idling, either the leaks are really large, or your compressor is worn, or the governor is set incorrectly, I side with leaks. HTH, George | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1216 Registered: 12-2000 Posted From: 76.66.19.52  Rating: N/A |
Yup, you got bad leaks. Don't drive that thing until you get your air system sorted out, and George is spot on, don't go under that bus unless you know how to block it up properly. We are waiting to help you. happy coaching! buswarrior | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 918 Registered: 10-2003 Posted From: 71.58.48.5  Rating: N/A |
Bart, does the coach sag at any of the corners when you run the engine or not? Would be an air bag or problem in the air leveling valve most likely in that case. When it hits about 60, does it then stay there or keep dropping to zero? If it stays at 60, then it would most likely be a leak in the air systems other that the brakes. Normally the air system pumps up the brake system first till about 60psi or so, then a protection valve opens and starts to fill the rest of the air system like air suspension and air operated wipers, kneeling system, air operated door, etc. This is to make sure you still have brakes in case you would have an air bag failure. The spring operated parking brakes give duplicate protection in case of a major air failure. If you need to get under the coach to locate the leak, you need to securely block up the coach at the reinforced body areas. You try to crawl under it without doing this and an air bag suddenly fails; the coach suddenly drops on you and you can be killed instantly or worse!Locating leaks is easier if you have an air line connected from a remote air compressor to your air tank or line. This way you don't have the noise of the engine trying to drown out the air leak noise. | ||
| Mark R. Obtinario (Cowlitzcoach)
Registered Member Username: Cowlitzcoach Post Number: 193 Registered: 4-2001 Posted From: 68.26.150.32 Rating: N/A |
Before you do anything to find the leak, make sure you block your bus up so that if an air bag should fail you have plenty of room between the bus and the ground. It is really hard to breathe with 40,000 pounds on your chest. I would echo what John said about diagnosing in what circuit the air leak is. As your go around your bus with your spray bottle, you will find a lot of little leaks. How many of them you decide to fix is sort of up to you. Just know that in a bus with an air suspension it is virtually impossible to get every leak stopped. I have seen 40-year old buses that didn't leak an ounce of air in 24-hours. On the other hand, I have seen buses less than 10-years old leak down to zero in less than two hours. The more air operated accessories the vehicle has the more potential for leaks you have. The leaks for which you will be looking will be the ones that are really leaking out the compressed air. If you can hear it leak it will need to be repaired. Oh, by the way, in case you haven't gotten the message yet, DO NOT GET UNDER THE BUS UNLESS IT IS BLOCKED UP HIGH ENOUGH THAT IF AN AIR BAG SHOULD FAIL IT WON'T SQUASH YOU FLAT! Mark O. Castle Rock, WA | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 378 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Bart, We're all on you about blocking the bus up, and please take that to heart! I'm not so much worried about a catastrophic air bag failure, as I am about the bus just settling down on you as the air leaks out. Believe me, it WILL happen. It may pin you in a minute or so, and take another ten minutes to crush you, as the air leaks out of the system. I didn't go into explaining the air system as John did, because you're not that far along yet, but here goes, and maybe this will help you understand how important proper blocking is! Most buses have a protection valve which opens between 80-90psi, and lets air into the auxiliary portion of the system, (air bags, wipers, door opener, etc.) Under that pressure, all of the air is kept in the brake reservoirs, for safety reasons, and most gauges read the brake reservoir pressure. This explains why when you start a bus, the pressure builds to 80-90 quickly, then slows down when the protection valve allows air into the auxiliaries, and it takes a lot of air to raise a deflated bus. The leveling valves are connected between the body and the axle, and let air into the bags until the bus rises to the height setting. Now, you air up the bus, it stands up, and you shut the engine off to hear the leaks better. While you are under, one of the leveling valves wants to let a little more air into one of the bags, and starts to take air from the auxiliary reservoir to do this. Since you have described at least two leaks, there may not be any more pressure in the auxiliary res than there is in the bag, and at that point, the bus will start to settle, and if you're under it, or leaning on the front tire looking underneath, you WILL be crushed between the tire and the underside of the body. If you are trying to tighten a leaking air bag or leveling valve fitting, and the line comes off, the bus will drop on you in one second. Please read Mark's last 2 paragraphs, and take them to heart! George | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1175 Registered: 5-2001 Posted From: 65.74.66.116 Rating: N/A |
Bart, to fine tune what George has mentioned, I will add the following: The protection pressure on our coach is about 65 psi. The pressure gauge is connected to the AUXILIARY system. This means that the gauge stays at zero until there is enough pressure to operate the brakes. There is a check valve in each leveling valve that SHOULD prevent any air pressure from leaving an air bag and entering the supply system when it has less pressure than the air bag. This all applies to our stock 4106, and may not be true of your coach. I mention these things to show how some other coaches may be plumbed. For what it's worth. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 255 Registered: 10-2006 Posted From: 66.90.229.44 Rating: N/A |
If you hear the leak, closest is the air wipers and operating knobs. Wet the windshield (to not scratch it) and fiddle with the knobs. IF the coach has an air fill installed perhaps with shop air and the engine off listening will be easier. FF | ||
| Tony LEE (T_lee)
Registered Member Username: T_lee Post Number: 23 Registered: 11-2007 Posted From: 58.165.105.167 Rating: N/A |
Turning the front wheels to full lock and then switching the engine off once the bus has aired up will provide pretty good access to the front suspension to check for leaks in good safety as long as you are aware of possible pinch-points if the body should drop. You can also make a stethoscope by taping a bit of 1/4" hose to a bit of wood and waving the end around near air fittings while listening at the other end. Saves getting under the bus. | ||
| Bart Duncan (Bartman)
Registered Member Username: Bartman Post Number: 15 Registered: 11-2007 Posted From: 68.185.135.211 Rating: N/A |
guys - GOT IT! don't get crushed! I really appreciate all of the warnings and excellent advice! can anyone tell me the ballpark price of air bags and installation- yes, I'm new Thanks! Bart | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 617 Registered: 11-2005 Posted From: 208.54.200.113  Rating: N/A |
As FF says, the wiper valves and motors are notorious for leaking, especially the valves. The WW connectors are bad for this also. Sometimes all you have to do is hit the "Park" position a couple of times with the WW valves and the leaking stops. Did this for me. |